1. Field of the Invention
This invention relates to a method for fabricating a thin film magnetic head.
2. Related Art Statement
In the fabrication of a thin film magnetic head, normally, a second magnetic film serving as a top magnetic film is formed after a first magnetic film (bottom magnetic film), a gap film, an insulating film to support a coil film are formed on a wafer. Moreover, in the formation of the second magnetic film, a plate underfilm is formed over the surface of the wafer including the insulating film by a sputtering method, etc. Then, a photoresist is applied on the surface of the plate underfilm and is processed by a photolithography method to form a resistframe for the formation of the second magnetic film. Then, the second magnetic film is formed in the area enclosed by the resistframe by an electroplating, etc. With the formation of the second magnetic film utilizing the electroplating, another film is plated beyond the resistframe, but it is removed.
In the second magnetic film-forming process, however, there is a problem due to the resistframe because an exposing light in the photolithography process to form the resistframe is reflected at the surface of the plate underfilm and then, introduced beyond a photomask-defining area to expose the photoresist around the photomask-defining area, resulting in the degradation in pattern precision of the resistframe and thus, the second magnetic film.
The degradation in pattern precision of the resistframe becomes conspicuous at the pole portion, where the second magnetic film is opposed to the first magnetic film via the gap film. On the backward area from the pole portion is positioned the insulating film rising up with an inclination of a given angle from the surface of the gap film. The starting point of the rising up corresponds to a Throat Height zero point and the rising up angle corresponds to an Apex Angle.
The second magnetic film constitutes the pole portion parallel to the gap film and the first magnetic film up to the Throat Height zero point and then, rises up with an inclination of the Apex Angle toward the top surface of the insulating film from the Throat Height zero point.
Thus, in the fabrication of the resistframe for the formation of the second magnetic film by the photolithography process, the photoresist stuck on the inclined portion with the Apex Angle toward the top surface of the insulating film must be exposed.
In this case, the exposing light is reflected at the plate underfilm stuck on the inclined portion, and is partially introduced to the pole portion, which results in the exposed pattern of the pole portion different from that of the photomask, and thus, the pattern destruction in the portion of the resistframe corresponding to the pole portion.
The pattern destruction of the resistframe has large difficulty in developing recording density by narrowing recording track width up to not more than 1.0 μm.
In order to iron out the above-mentioned problem, it is proposed in Patent publication 1 that before the formation of the photoresist frame serving as a top magnetic film, an antireflection film is formed, and a photoresist is formed on the antireflection film, and the resistframe is formed from the photoresist through exposure and development.
The antireflection film, however, can not be dissolved in an alkaline developer to remove the resistframe, so it is required to be removed by means of ashing or the like after the formation of the resistframe using the alkaline developer. Then, after the removal of the antireflection film, the second magnetic film is formed by means of plating or the like. Therefore, in the formation of the second magnetic film using the antireflection film by means of the photoresist technique, a large number of processings are required.
Also, the antireflection film is formed over the inner pattern enclosed by the resistframe. The inner pattern includes a pole portion area corresponding to the pole portion of the top magnetic film and a second yoke area corresponding to the yoke portion. Therefore, the antireflection film must be removed in the pole portion area and the second yoke area.
In the resistframe, however, the pole portion area is quite different in opening area from the second yoke portion. In addition, for high density recording, the opening area of the pole portion area tends to be narrowed up to 1 μm or below. In the removal of the antireflection film stuck on the inner pattern enclosed by the resistframe, therefore, the second yoke area is quite different in etching rate from the pole portion area. Concretely, it takes long period of time in etching the pole portion area than the second yoke portion. As a result, at the removal of the antireflection film, the resistframe is etched largely at the pole portion area to enlarge the distance of the resistframe thereat. In other words, the distance of the resistframe is enlarged through the removal of the antireflection film. As a result, the antireflection film, which is formed inherently for narrowing the pole portion width, enlarges the resistframe distance, becoming an obstacle in the narrowing of the pole portion width.
An antireflection film soluble in a photoresist developer is proposed in Patent publication 2, which is suitable for ironing out the technical problem of Patent publication 1. Since the developing degree of the antireflection film depends on the frame width of an opening for a pole portion made by a photoframe which is formed on the antireflection film, if each frame width fluctuates on the same wafer, it may also fluctuate. For example, the antireflection film may be developed excessively at one opening so that it may be infiltrated under the photoresist, and the antireflection film may be developed insufficiently at another opening so that it remains partially in the inner bottom surface of the opening.
[Patent Publication 1]
Japanese patent application Laid-open No. 9-180127
[Patent Publication 2]
Japanese patent application Laid-open No. 2000-314963